Sale of Accounts Receivable (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Transfers and Servicing [Abstract]
Maximum amount provided under accounts receivable securitization facility excluded in lines of credit	$ 1,000,000,000		$ 1,000,000,000
Receivables sold under securitization facility derecognized during the period	1,500,000,000		1,500,000,000
Cash payments received in exchange for the transfer of accounts receivable			1,000,000,000
Deferred receivables consideration	546,000,000		546,000,000		900,000,000
Proceeds received in cash from transfers of receivables to purchasers			18,900,000,000	8,900,000,000
Cash collections on deferred consideration			18,900,000,000	8,900,000,000
Loss on transfer of accounts receivables to purchasers	$ 1,000,000	$ 3,000,000	$ 2,000,000	$ 4,000,000